IgG4 Contactin-1 Autoimmune Nodopathy: A Case Report

Case Diagnosis: IgG4-mediated Autoimmune Nodopathy

Case Description or Program Description: A 46-year-old female with a history of substance abuse was referred to the electrodiagnostics laboratory with one month of rapidly progressive asymmetric quadriparesis, difficulty ambulating, sensory loss and paresthesia. Electrodiagnostic testing revealed a generalized axonal sensorimotor neuropathy with diffuse, severe sensorimotor axonal loss but no evidence of demyelination. She was referred to a tertiary center neuromuscular department, who admitted her due to the tetraparesis and new onset of dysphagia. Extensive workup identified contactin-1 antibodies and she was diagnosed with contactin-1 autoimmune neuropathy. Patient was started on Rituximab and Solu-medrol therapy with good response with overall arrest of the disease and some recovery. Following hospitalization, she was admitted to acute inpatient rehab. Presently, she continues to receive these treatments with sustained improvement.

Setting: Outpatient electrodiagnostic laboratory

Assessment/Results: Electrodiagnostics during hospitalization showed severe end-stage sensory and motor radiculoneuropathy. Cerebrospinal fluid analysis revealed presence of contactin-1 antibodies, markedly elevated total protein (261), cell count (mono/macro 47%), IgG (32.12), albumin (152.6), and IgG synthesis rate (69.80). Imaging showed diffuse enhancement of the trigeminal nerve and cauda equina.

Discussion (relevance): Contactin-1 antibody-associated autoimmune neuropathy is a rare neuropathy characterized by severe, rapidly progressive onset with predominantly motor symptoms and early axonal involvement that can mimic autoimmune demyelinating neuropathies but has distinct clinical and electrodiagnostic features. As an IgG4-mediated process, it is typically unresponsive to IVIG, but responds well to high-dose corticosteroids and Rituximab.

Conclusions: This case highlights IgG4 Contactin-1 autoimmune nodopathy, a rare and often under-recognized neuromuscular disorder that physiatrists may encounter in clinical practice. Given its treatable nature, early identification and prompt intervention are crucial.